Marking of roadways



Nov. 2, 1965 R. JR 3,215,051

MARKING OF ROADWAYS Filed Dec. 1. 1961 1/ 20 /s 2/ a my INVENTOR f dwm/ 61/1 44 BY \ZRRL. (J. we

ATTORNEY United States Patent 3,215,051 MARKING OF ROADWAYS Edwin R. Gill, J12, Hiddenhurst-Coleman Station, Millerton, N.Y. Filed Dec. 1, 1961, Ser. No. 156,435 6 Claims. (Cl. 94-15) The present application is a continuation-in-part of my copending application Serial No. 805,010 filed April 8, 1959, now abandoned.

This invention relates to the surface marking of highway surfaces and more particularly to a method of marking and the resulting structure obtained for improving the visibility of black top paving.

The great majority of primary highways in this country are usually surfaced with either concrete or the so-called black top paving. The black top paving as used herein refers to any suitable asphaltic or coal tar composition.

The concrete highways being of a light color, are readily visible, even when wet, and the outer edges of the pavement are distinguishable from the shoulders of the roadway even at night. Bituminous mixes, however, being of a dark coloration, usually black, are at a distinct disadvantage when compared to concrete as regards visibility at night. When a black top roadway is wet this is especially true. The outer edges of the black top pavements have very poor definition even in clear weather. It has previously been suggested to apply reflectorized marking materials to the outer edges of the roadway and as lane lines to separate the highway into lanes.

An object of the present invention is to provide a method of improving the visibility of black top pavements.

Another object of the present invention is to provide a black top pavement of improved night time visibility.

A still further object of the present invention is to provide an improved black top roadway wherein the traffic lanes are clearly visible at night and yet the day time appearance is not affected.

Another object of the present invention is to provide an improved black top roadway of multiple lanes wherein the running and passing traflic lanes are clearly distinguishable at night.

A still further object of the present invention is to provide an improved highway marking system which provides a carpet of light for guiding motorists.

Other objects and the nature and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of a two-lane highway treated in accordance with the present invention;

FIG. 2 is a similar view of a four-lane highway treated in accordance with the present invention;

FIG. 3 is a partial cross sectional view of a portion of the roadway greatly enlarged showing the spheres before and after they have been subjected to traffic;

FIG. 4 is a cross sectional view taken along the line 44 of FIG. 1; and

FIG. 5 is a cross sectional view taken along the line 55 of FIG. 2.

In accordance with the present invention, the center portions of the highway lanes are rendered reffective at night to yield a carpet of light to guide motorists, the amount of reflectively of the riding lanes being appreciatively less than the reflectivity of the lane lines, and the daylight appearances of the roadway being unaffected.

This is accomplished by covering the center portions of the lanes of black top pavements with small reflectively coated glass spheres partially embedded therein. As shown in FIG. 1, the highway surface is separated by a center line 12 into two traffic lanes 14 and 16.

The center lane line 12 is a conventional line as is "ice widely used in highway marking. These lane lines include a plurality of reflecting units such as glass beads partially embedded in a reflecting binder. The amount of glass beads used in such lane lines is approximately 3 to 8 pounds of beads per gallon of paint. The marking paint will yield a lane line 4 inches wide and approximately 400 feet long having a thickness of about 15 mils. If the glass beads have an average diameter of 15 mils, then six pounds of beads per gallon of paint will yield a density of beads of about 780 points of light per square inch of roadway. If eight pounds of beads are used per gallon of paint, a density of beads of about 1043 points of light per square inch of roadway will be obtained. This is referred to hereafter as a concentrated amount of reflecting units per unit area.

Each traffic lane is sprinkled with a dispersed amount of glass spheres 18, which are then rolled into the black top with suitable heat and pressure. The heat is used when necessary in cold weather to soften the surface and facilitate penetration of the glass spheres. The glass spheres may be made of glass having a relatively high index of refraction, namely, 1.90 or greater, so that the light is refracted back from within the spheres. Alternately, the glass spheres may be coated with a reflecting coating or thin shell 20 completely encasing each sphere.

The coating or shell 20 may be of silver, mercury, aluminum or other suitable metal or alloy and may be formed by vacuum deposition, sputtering, spraying or other means. Instead of metal, a pigmented plastic or other pigmented reflecting coating material may be used to coat the spheres.

The spheres are extremely small having an average diameter of approximately /2-30 mils. The spheres are scattered onto the surface of the road, and excellent results are obtained even though the spheres are widely separated from one another, as contrasted with the lane lines wherein the glass spheres are virtually in contact with one another.

When the spheres have been partially embedded in the black top surface, they will appear as shown on the left,

of FIG. 3. However, the abrasion of traflic soon wears off the upper exposed portion of the coating as shown at the right in FIG. 3, so as to permit reflex reflection of light from the headlights of approaching traflic.

If desired, for immediate reflex reflection, the coating from the upper exposed surfaces of the spheres can be removed by use of a suitable solvent or any other means.

Of course, when the high index of refraction glass is used in place of the reflectively coated glass spheres, then immediate reflex refraction is obtained without the necessity of removal of any coating.

It is extremely important that the spheres applied to the lanes be appreciably more dispersed than the spheres which are incorporated in the lane lines. It is essential that there be a good contrast between the so-called carpet of light in the lanes and the highly reflective lane lines. Accordingly, it is contemplated that the weight of the glass spheres in the carpet of light per unit area will be approximately to /2 the weight of the glass spheres in the same areas of lane lines. Preferably, the weight of the glass spheres in the lanes per unit area will be to A the weight of the glass spheres in the same area of lane lines.

As shown in the drawings, the spheres are applied only to the central portion of each lane leaving a border 21 at each outer edge. Thus, for example, a margin of a foot, more or less, left on each side of the reflectorization serves as an additional safety factor because of the instinctive tendency of the driver to center his vehicle on the most visible portion of the lane.

The usual conventional center line 12 may be employed which includes a pigmented reflecting composition coated with 3-8 pounds of the usual small glass spheres per gallon of paint. In a four-lane highway, as shown in FIG. 2, additional discontinuous lane lines 22 are shown dividing each half of the highway into running and passing lanes. Where it is desired to differentiate between the running and passing lanes, as for example in a three or four lane highway, the treatment of the surfaces can be varied. For example, the refiectively coated glass spheres distributed over the running lanes may be identified by reflected light of a tint or color which differs from the tint or color of the light reflected by the spheres distributed over the passing lanes. This differentiation may be accomplished byvarious means such as varying the color or tint of the glass, the type of coating, the color of the coating material or by varying the index of refraction of the two glasses. Combinations of these expedients can be employed.

Glass spheres having an index of the refraction of about 1.5-1.7 are known to reflect the color of the reflecting coating adjacent to the lower surface of the spheres, whereas glass spheres having an index of 1.90 or greater are known to reflect a silvery white regardless of the color of the reflecting coating. Thus, the different effects in different tr'aflic lanes can be controlled.

In treating a bituminous surface of a roadway according to this invention the refiectively coated glass spheres are distributed in the predetermined ratio to area over the proper width of the lane, and the spheres are then rolled in with suitable pressure until they are partially embedded. Heat may be applied in cold weather to soften the upper surface, or if desired the glass spheres can be applied when the highway is first laid before it has completely cooled.

The refiectively coated spheres may be made of glass or the equivalent so long as the material is transparent, has the proper index of refraction and is resistant to the abrasion of traflic.

As a specific example, a roadway is uniformly covered with glass spheres having an index of refraction of 2.0. The glass spheres are applied in a ratio of 8 pounds of glass spheres per 400 feet of a lane approximately 8 feet wide. The glass spheres have an average diameter of approximately 15 mils and a density of approximately 5. This yields a coverage of the road surface of approximately 256 points of light (glass spheres) per square inch of area. This is approximately of the weight of the glass spheres per square inch of the lane line.

It has been found that when the critical amount of glass spheres is utilized in the lanes, the daylight appearance of the roadway is not changed, nor are the riding characteristics of the roadway significantly changed. At night, in viewing the road, the lane line reflects brilliantly due to. the headlights, whereas the riding lane itself reflects by contrast as a 'less intense carpet of light. The lane lines or edge deleneators must be as brilliant as possible so that they appear to be traveller to be a solid line of brilliance throughout their observable length so that they can be seen as far in advance as possible. By contrast, with these brilliant lane lines, the usual black top road becomes substantially invisible. In accordance with the present invention, the reflecting units are so dispersed throughout the riding lane that although the daylight appearance of the road is not affected, at night, the lane will be visible by a reflex reflection of the light from the headlights.

It will be obvious to those skilled in the art that various changes may be made without departing from the spirit of the invention and therefore the invention is not limited to what is shown in the drawings and described in the specification, but only as indicated in the appended claims.

What is claimed is:

1. A roadway having an upper asphalt black topped surface with an improved night-time visibility without substantially changing its daylight appearance comprising at least one reflex reflecting lane line on said upper surface dividing the roadway into traflic lanes, said lane lines being visible in daylight and brilliantly reflex reflecting at night, said lane lines containing a concentrated amount of small spherical reflecting units, each having a diameter of /2-30 mils, partially embedded in a reflecting binder, and a plurality of small spherical reflecting units each having a diameter of /2-30 mils partially em bedded into the upper surface of each said traflic lane, said latter reflecting units being relatively dispersed with respect to each other so as to be relatively invisible in daylight, said latter reflecting units being partially embedded into virtually the entire width of the traflic lane and extending continuously longitudinally along the traffic lane so as to reflect back light at night as a continuous carpet of light covering the traflic lane for guiding motorists.

2. A roadway in accordance with claim 1 wherein said partially embedded reflecting units cover virtually the entire width of the traffic lane but are omitted from the outer edges of said lane to leave a narrow border at each edge of the lane without units partially embedded therein.

3. A roadway in accordance with claim 1 wherein the weight of the reflecting units partially embedded. in the traflic lanes per unit area are approximately to /2 the weight per unit area of the reflecting units in the adjacent lane line.

4. A roadway in accordance with claim 1 wherein the weight of the reflecting units partially embedded in the traflic lane per unit area are approximately /2 to A the weight per unit area of the reflecting units in the adjacent lane.

5. A roadway in accordance with claim 1 wherein said partially embedded reflecting units are reflex reflecting glass beads which are refiectively coated on the embedded portions thereof.

6. A roadway in accordance with claim 1 wherein said partially embedded reflecting units are glass beads having an index of refraction of at least 1.90.

References Cited by the Examiner UNITED STATES PATENTS 2,070,432. 2/37 Huebscher 941.5 2,345,644 4/44 Weber 941.5 2,355,430 8/44 Flood 941.5 2,366,715 1/45 French 941.5 2,574,971 11/51 Heltzer 941.5 X 2,838,408 11/58 Rindone 941.5 2,882,632 4/59 Rockwell et a1. 941.5 2,963,378 12/60 Palmquist 941.5 3,103,859 9/63 Dye 94-1.5 X

OTHER REFERENCES Manual of Uniform Traflic Control Devices For Streets And Highways by Public Road Administration, August 1948, HE/370/J65/C-4, pages 76, 87, and 94.

Municipal South, February 1960, pages 17, 18, and 20.

CHARLES E. OCONNELL, Primary Examiner. JACOB. L. NACKENOFF, Examiner. 

1. A ROADWAY HAVING AN UPPER ASPHALT BLACK TOPPED SURFACE WITH AN IMPROVED NIGHT-TIME VISIBILITY WITHOUT SUBSTANTIALLY CHANGING ITS DAYLIGHT APPEARANCE COMPRISING AT LEAST ONE REFLEX REFLECTING LANE LINE ON SAID UPPER SURFACE DIVIDING THE ROADWAY INTO TRAFFIC LANES, SAID LANE LINES BEING VISIBLE IN DAYLIGHT AND BRILLIANTLY REFLEX REFLECTING AT NIGHT, SAID LANE LINES CONTAINING A CONCENTRATED AMOUNT OF SMALL SPHERICAL REFLECTING UNITS, EACH HAVING A DIAMETER OF 1/2-30 MILS, PARTIALLY EMBEDDED IN A REFLECTING BINDER, AND A PLURALITY OF SMALL SPHERICAL REFLECTING UNITS EACH HAVING A DIAMETER OF 1/2-30 MILS PARTIALLY EMBEDDED INTO THE UPPER SURFACES OF EACH SAID TRAFFIC LANE, SAID LATTER REFLECTING UNITS BEING RELATIVELY DISPERSED WITH RESPECT TO EACH OTHER SO AS TO BE RELATIVELY INVISIBLE IN DAYLIGHT, SAID LATTER REFLECTING UNITS BEING PARTIALLY EMBEDDED INTO VIRTUALLY THE ENTIRE WIDTH OF THE TRAFFIC LANE AND EXTENDING CONTINUOUSLY LONGITUDINALLY ALONG THE TRAFFIC LANE SO AS TO REFLECT BACK LIGHT AT NIGHT AS A CONTINUOUS CARPET OF LIGHT COVERING THE TRAFFIC LANE FOR GUIDING MOTORISTS. 